#include <iostream>
#include <math.h>
using namespace std;

class point
{
private:
	int x;
	int y;
public:
	//构造函数
	point(int x=0,int y=0):x(x),y(y){}
	friend double ret(const point&a,const point&b)
	{
		double ret=sqrt((b.x-a.x)*(b.x-a.x)+(b.y-a.y)*(b.y-a.y));
		return ret;
	}
};
int main()
{
	point a;//默认构造x=0,y=0
	point b(3,4);
	point c=point(5,5);
	cout << ret(a,b) << endl;
	cout << ret(a,c) << endl;

	return 0;
}
